A multigate device or multiple gate field effect transistor (MuGFET) is a metal-oxide-semiconductor field effect transistor (MOSFET) that incorporates more than one gate into a single device.
One particular type of multigate device is the finFET, which refers to a nonplanar, multi-gate transistor built on a silicon-on-insulator (SOI) substrate and based on the earlier DELTA (single-gate) transistor design. A distinguishing characteristic of the finFET is a conducting channel in a thin silicon “fin,” which forms the body of the device.
Another type of multigate device is the tri-gate or three-dimensional (3D) transistor (not to be confused with a 3D microchip) fabrication used for the nonplanar transistor architecture used in certain processors (e.g., processors based on the 22 nanometer manufacturing process). Tri-gate transistors employ a single gate stacked on top of two vertical gates, creating additional surface area for carriers to travel.
The performance of finFET and tri-gate devices is severely limited by high external resistance (Rext) and interface state density (Dit). Rext is difficult to solve in III-V types of finFET and tri-gate devices, owing to the difficulty in forming high-quality contacts due to limited thermal budget of processing. Dit is also difficult to solve in III-V types of finFET and tri-gate devices, owing to a high concentration of interface states at the oxide/semiconductor interface.